Taking a lunch break during a search for orchids in the Austrian countryside.

‘Agricultural practices are not necessarily at fault here – but our choice of food is’

Staff Report

FRISCO — Forget about greenhouse gas pollution from factories and transportation — by 2050 emissions of carbon dioxide and methane from food production alone could exceed targets set to prevent catastrophic global warming, University of Cambridge scientists warn in a new paper.

A major shift in food consumption norms has to be a big part of an overall plan to cut atmospheric concentrations of heat-trapping air pollution, especially given the current trend toward meat-heavy Western diets, the authors wrote in the journal Nature Climate Change.

With the global population expected to surge near the 10 billon mark by mid-century, there will be more pressure to cultivate more land, increasing carbon emissions, deforestation and biodiversity loss. By 2050, cropland will have expanded by 42 percent and fertiliser use increased sharply by 45 percent over 2009 levels. A further tenth of the world’s pristine tropical forests would disappear over the next 35 years.

The study shows that increased deforestation, fertilizer use and livestock methane emissions are likely to cause GHG from food production to increase by almost 80%. This will put emissions from food production alone roughly equal to the target greenhouse gas emissions in 2050 for the entire global economy.

“There are basic laws of biophysics that we cannot evade,” said lead researcher Bojana Bajzelj from the University of Cambridge’s Department of Engineering, who authored the study with colleagues from Cambridge’s departments of Geography and Plant Sciences as well as the University of Aberdeen’s Institute of Biological and Environmental Sciences.

“The average efficiency of livestock converting plant feed to meat is less than 3 percent, and as we eat more meat, more arable cultivation is turned over to producing feedstock for animals that provide meat for humans. The losses at each stage are large, and as humans globally eat more and more meat, conversion from plants to food becomes less and less efficient, driving agricultural expansion and land cover conversion, and releasing more greenhouse gases. Agricultural practices are not necessarily at fault here – but our choice of food is,” said Bajzelj.

“It is imperative to find ways to achieve global food security without expanding crop or pastureland. Food production is a main driver of biodiversity loss and a large contributor to climate change and pollution, so our food choices matter.”

The team analyzed evidence such as land use, land suitability and agricultural biomass data to create a robust model that compares different scenarios for 2050, including scenarios based on maintaining current trends.

One scenario investigated by the team is on the supply side: the closing of ‘yield gaps’. Gaps between crop yields achieved in ‘best practice’ farming and the actual average yields exist all over the world, but are widest in developing countries – particularly in Sub-Saharan Africa. The researchers say that closing these gaps through sustainable intensification of farming should be actively pursued.

The scientists also looked closely at food waste, finding it at all stages of the food chain. In developing countries, poor storage and transportation cause waste; in the west, wasteful consumption is rife.

“The latter is in many ways worse because the wasted food products have already undergone various transformations that require input of other resources, especially energy,” said Bajzelj.

“Western diets are increasingly characterised by excessive consumption of food, including that of emission-intensive meat and dairy products. We tested a scenario where all countries were assumed to achieve an average balanced diet – without excessive consumption of sugars, fats, and meat products. This significantly reduced the pressures on the environment even further,” said the team.

The ‘average’ balanced diet used in the study is a relatively achievable goal for most. For example, the figures included two 85g portions of red meat and five eggs per week, as well as a portion of poultry a day.

“This is not a radical vegetarian argument; it is an argument about eating meat in sensible amounts as part of healthy, balanced diets,” said Cambridge co-author Prof Keith Richards. “Managing the demand better, for example by focusing on health education, would bring double benefits – maintaining healthy populations, and greatly reducing critical pressures on the environment.”

Co-author Prof Pete Smith from the University of Aberdeen said: “unless we make some serious changes in food consumption trends, we would have to completely de-carbonise the energy and industry sectors to stay within emissions budgets that avoid dangerous climate change. That is practically impossible – so, as well as encouraging sustainable agriculture, we need to re-think what we eat.”

David Petraeus, the former CIA director and top Army general whose affair with his biographer brought down what many considered a bright political future, has agreed to plead guilty to mishandling classified materials.